Mitigation of Voltage and Frequency Excursions in Low-Inertia Microgrids

Power systems proliferated by distributed generation sources are becoming increasingly prone to frequency and voltage disturbances. These problems are exacerbated in microgrids since they have fewer intrinsic disturbance-rejecting measures and features. To increase the reliability and stability of emerging power systems, the advanced control structures of the distributed generation sources based on power electronics devices must be deployed during suboptimal operating conditions. The aggravating circumstance is that both voltage and frequency excursion can be transient and long-lasting and consequently can occur simultaneously. The algorithm proposed in this paper integrates voltage support (nominal voltage restoration) and inertia emulation features with the comprehensive current references management scheme, thus securing improved grid operating conditions during several different faults and occurrences. The control algorithm is developed and tested in the context of a small microgrid, but it can be applied with minimal alterations in traditional grids, also. To prove that it is possible to decrease simultaneously voltage unbalances and frequency deviations, a test microgrid consisting of a synchronous generator, photovoltaic system, battery storage system, and controllable balanced and unbalanced loads was developed in a hardware-in-the-loop environment.